This invention relates to a thermoplastic polymeric resin which is a polyblend of a thermoplastic aromatic polycarbonate and a thermoplastic polyurethane.
Thermoplastic polycarbonate resins are readily molded at elevated temperatures to make a wide variety of articles. Exemplary of such articles are automotive parts, tool housings, structural components and the like. The use of polycarbonate on its own for molding purposes is limited as the polycarbonate has a number of deficiencies including sensitivity of impact toughness to the ambient temperature and more particularly thickness of the molded article, and susceptibility to degradation by solvents including water and hydrocarbons.
Correction of the deficiency of polycarbonate resins is known by blending the polycarbonates with other polymeric additives, as disclosed in U.S. Pat. No. 3,431,224, and addition of other compounds and stabilizers, as disclosed in U.S. Pat. Nos. 3,498,946 and 3,742,083.
Polycarbonate resins have been modified by blending with other polymers including polyethylene, polypropylene, copolymers of ethylene and an alkyl acrylate, polyamide, polyvinyl acetate, alkyl cellulose ether and polyurethane elastomer.
In U.S. Pat. No. 4,034,016 a ternary blend consisting of a polycarbonate, a polybutylene terephthalate and a thermoplastic polyurethane (hereafter referred to as TPU) is disclosed having an improved impact strength at critical thickness. U.S. Pat. No. 4,179,479 discloses a ternary blend of a TPU, a thermoplastic polycarbonate and an acrylic polymer: the latter functioning as a processing aid to confer uniformity of melt flow properties. U.S. Pat. No. 4,350,799 discloses a ternary blend containing a TPU, a polycarbonate and a polyphosphate, the blend displays reduced flammability. Ternary blends of TPU, polycarbonate and rubbers as impact modifiers are disclosed by EP 125739 and U.S. Pat. No. 4,522,979.
The preparation of binary TPU, polycarbonate blends has been little studied due to the inherent problems of compatibility between polycarbonate and TPU including, for example, large differences in melt viscosities, processing temperatures and thermodynamic solubilities. These differences are especially prominent with polyether-based TPUs.
In a recent publication, U.S. Pat. No. 4,743,650, binary blends containing polycarbonate and from 5 to about 35 parts by weight of a polyether polyol-based TPU are claimed.
Accordingly, it would be desirable to provide a binary polycarbonate, TPU blend wherein the incompatibility difference of the two polymers has been minimized and wherein molded articles prepared therefrom show improved resistance to hydrocarbon solvents and improved impact resistance and toughness compared to polycarbonate alone.